Image rotation method and image rotation processing apparatus

Abstract

An image rotation method and an image rotation processing apparatus in an image processing apparatus are disclosed. The image rotation method obtains the image coordinates (x',y') of a rotated image which is recorded in a second memory, by sequentially scanning a first memory where the M×N original image is recorded and adding the increments of x and y corresponding to a rotation angle θ repeatedly, and transmits the image element data of the coordinates (x,y) of the first memory to the coordinates (x',y') of the second memory with one-to-one correspondence, thereby obtaining the rotated image through the rotation angle θ from the original image. Thus, the present invention can obtain the rotated image using only addition operations and without any multiplication operations, so that high-speed operation is possible and an image can be rotated through a specified angle θ through software in common computer graphic systems having no floating point multiplier.

What is claimed is: 
     
       1. An image rotation processing apparatus which rotates an image of a magnitude of M×N, recorded in a first memory according to any rotation angle θ which lies between 0 and 360 degrees by generating rotation coordinates (x', y') of the first memory in order to record the image in a second memory, said apparatus comprising: an address generator for generating image coordinates (x,y) of the first memory corresponding to a given image magnitude, M×N, by linear sequential scanning; and   an address converting circuit including an adder for accumulating increments of values of coordinates (x', y') of the second memory according to the increments of the values of the coordinates (x,y) of the first memory in correspondence with a rotation angle θ, to generate the coordinates (x', y') of the second memory corresponding to the coordinates (x,y) of the first memory.   
     
     
       2. An image rotation processing apparatus as claimed in claim 1, wherein said address converting circuit comprises: a first accumulator means for accumulating a cosine value (cos=n) corresponding to the rotation angle θ of a unit value of the value x of the first memory whenever the value x is incremented by one;   a second accumulator means for accumulating a sine value (sin=m) corresponding to the rotation angle θ of the unit value of the value x of the first memory whenever the value x is incremented by one;   a third accumulator means connected to said first accumulator means for adding a negative sine value (-sin=-m) corresponding to the rotation angle θ of a unit value of the value y of the first memory into the output value of said first accumulator means and accumulating said negative sine value (-m) into the added value whenever the value y is incremented by one, to determine the value of the coordinate x' of the second memory; and   a fourth accumulator means connected to said second accumulator means for adding the cosine value (cos=n) corresponding to the rotation angle θ of the unit value of the value y of the first memory into the output value of said second accumulator means and accumulating the cosine value (n) into the added value whenever the value y is incremented by one, to determine the value of the coordinate y' of the second memory.   
     
     
       3. An image rotation processing apparatus as claimed in claim 2, wherein each of said first and second accumulator means comprises: a first adder for adding the cosine value (n) or the sine value (m) to an accumulated result value;   a first register connected to said first adder which records the accumulated result of said adder;   feedback means interconnecting said first register and said first adder for feeding the accumulated result value from said first register to said first adder whenever the value of x is incremented by one; and   a transmitting gate connected to said first adder which transmits the added result of said first adder whenever the value of x is incremented by one.   
     
     
       4. An image rotation processing apparatus as claimed in claim 3, wherein each of said third and fourth accumulator means comprises: a second adder for adding said negative sine value (-m) or cosine value (n) to an accumulated result value;   a second register connected to said second adder which is initialized to the transmitted added result supplied from said first or second accumulator means whenever the value x is incremented by one and which records the added result of said second adder whenever the value y is incremented by one;   feedback means interconnecting said second register and said second adder for feeding the accumulated result value back into said second adder; and   a transmitting gate for transmitting the added result of said second adder to the value of the coordinate x' or y' of the second memory whenever the value y is incremented by one.   
     
     
       5. An image rotation processing apparatus which rotates an M×N image, said apparatus comprising: a first accumulator circuit for accumulating the cosine value corresponding to a rotation angle θ of the unit value of the coordinate value x;   a second accumulator circuit for accumulating the sine value corresponding to the rotation angle θ of the unit value of the coordinate value x;   a third accumulator circuit for adding the negative sine value corresponding to the rotation angle θ of the unit value of the coordinate value y to an output of said first accumulator circuit, and summing the negative sine value with the added value to determine the value of the rotated coordinate x'; and   a fourth accumulator circuit for adding the cosine value corresponding to the rotation angle θ of the unit value of the coordinate value y to an output value of said second accumulator circuit and summing the cosine value with the added value to determine the value of the rotated coordinate y'.   
     
     
       6. An image rotation processing circuit which rotates on M×N image through a rotation angle θ, said circuit comprising: a first adder having first and second inputs and an output;   a first register connected to the output of said adder which stores the output from said first adder;   means for supplying a cosine value (n) of the rotation angle θ as the first input to said first adder;   feedback means interconnecting said first register and said adder for supplying the contents of said first register as the second input to said first adder;   a first transmitting gate connected to said first adder which transmits the output of said first adder;   a second adder having first and second inputs and an output;   means for supplying a negative sine value (-m) of the rotation angle θ to the adder as the first input;   a second register connected to said first transmission gate and the output of said second adder;   feedback means interconnecting said second adder and said second register for supplying the contents of said second register as the second input to said second adder;   a second transmitting gate connected to said second adder which transmits the output of said second adder responsive to a control signal to produce a rotational coordinate x';   a third adder having first and second inputs and an output;   a third register connected to the output of said adder which stores the output from said third adder;   means for supplying a sine value (m) of the rotation angle θ as the first input to said third adder;   feedback means interconnecting said third register and said third adder for supplying the contents of said third register as the second input to said third adder;   a third transmitting gate connected to said third adder which transmits the output of said third adder;   a fourth adder having first and second inputs and an output;   means for supplying the negative sine value (-m) to the adder as the first input;   a fourth register connected to said first transmission gate and the output of said fourth adder;   feedback means interconnecting said fourth adder and said fourth register for supplying the contents of said fourth register as the second input to said fourth adder;   a fourth transmitting gate connected to said fourth adder which transmits the output of said fourth adder responsive to a second control signal to produce a rotational coordinate y'.